Loudspeaker

ABSTRACT

A loudspeaker has a frame, a magnetic circuit, a voice coil body, a first edge, a diaphragm, a second edge, and a damper. The magnetic circuit is provided with a magnetic gap, and is supported by the frame. The voice coil body is disposed movably with respect to the magnetic gap. The outer peripheral end of the diaphragm is coupled to the frame via the first edge, and the inner peripheral end thereof is coupled to the voice coil body. The second edge is coupled to the frame at a position closer to the magnetic circuit than the first edge. The damper is disposed closer to the magnetic circuit than the diaphragm, the outer peripheral end thereof is coupled to the frame via the second edge, and the inner peripheral end thereof is coupled to the voice coil body.

TECHNICAL FIELD

The present invention relates to a structure for improving the drivingefficiency of a loudspeaker of low acoustic strain.

BACKGROUND ART

FIG. 3 is a diagram showing a part of a cross section of a conventionalloudspeaker. In this loudspeaker, voice coil body 22 movably disposed onmagnetic circuit 21 is coupled to the inner peripheral end of diaphragm23. The outer peripheral end of diaphragm 23 is coupled to frame 25 viaedge 24. The back surface of diaphragm 23 is coupled to frame 25 viasuspension holder 26 and edge 27. The projecting shapes of edges 24 and27 are pointed to opposite directions, and hence the upside and downsideof the amplitude of diaphragm 23 are vertically symmetric. Thus, theacoustic strain of the loudspeaker is reduced. Such a loudspeaker isdisclosed in Japanese Patent Unexamined Publication No. 2004-7332, forexample.

In such a loudspeaker structure, suspension holder 26 is formed of arigid body with a rigidity equivalent to that of diaphragm 23.Therefore, the additional mass of diaphragm 23 is increased, and hencethe driving load is increased on magnetic circuit 21. As a result, it isdifficult to improve the driving efficiency of the loudspeaker.

SUMMARY OF THE INVENTION

The present invention can further improve the driving efficiency of aloudspeaker of low acoustic strain. The loudspeaker of the presentinvention has a frame, a magnetic circuit, a voice coil body, a firstedge, a diaphragm, a second edge, and a damper. The magnetic circuit isprovided with a magnetic gap, and is supported by the frame. The voicecoil body is disposed movably with respect to the magnetic gap. Theouter peripheral end of the diaphragm is coupled to the frame via thefirst edge, and the inner peripheral end thereof is coupled to the voicecoil body. The second edge is coupled to the frame at a position closerto the magnetic circuit than the first edge. The damper is disposedcloser to the magnetic circuit than the diaphragm, the outer peripheralend of the damper is coupled to the frame via the second edge, and theinner peripheral end thereof is coupled to the voice coil body. Thisstructure can suppress the acoustic strain of the loudspeaker andimprove the driving efficiency thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a part of a cross section of a loudspeakerin accordance with an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a part of a cross section of anotherloudspeaker in accordance with the exemplary embodiment of the presentinvention.

FIG. 3 is a diagram showing a part of a cross section of a conventionalloudspeaker.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 is a diagram showing a part of a cross section of a loudspeakerin accordance with an exemplary embodiment of the present invention.Magnetic circuit 1 is disposed in the center of the bottom of bowl-likeframe 5, namely it is supported by frame 5. Magnetic circuit 1 is formedby combining and sticking disk-like magnet 1A, disk-like plate 1B, andcylindrical yoke 1C having a closed-end. Magnetic gap 8 is formedbetween the inner peripheral side face of a side wall part of yoke 1Cand the outer peripheral side face of plate 1B so as to open toward theupper face side of magnetic circuit 1. In other words, magnetic gap 8opens toward diaphragm 3.

Voice coil body 2 is structured by winding a coil (not shown) on theouter periphery of cylindrical support body 2A. Voice coil body 2 isdisposed vertically movably with respect to magnetic gap 8, and vibratesdiaphragm 3 coupled to the outer periphery of the upper part of voicecoil body 2. Dust cap 9 for dust-proofing is disposed at the upper endof voice coil body 2.

Diaphragm 3 is a part functioning as a sound source of a loudspeaker,and is mainly made of pulp and resin for establishing high rigidity andinternal loss. The outer peripheral end of diaphragm 3 is coupled to theopening end of frame 5 via first edge (hereinafter referred to as“edge”) 4 projecting upward. The inner peripheral end of diaphragm 3 isfixed to voice coil body 2. Edge 4 is made of urethane, foamed rubber,styrene butadiene rubber (SBR), or cloth in order to prevent a load frombeing applied to movement of diaphragm 3.

Damper 10 is disposed closer to magnetic circuit 1 than diaphragm 3. Theinner peripheral end of damper 10 is coupled to voice coil body 2 at aposition closer to magnetic circuit 1 than the position at whichdiaphragm 3 is fixed to voice coil body 2. The outer peripheral end ofdamper 10 is coupled to frame 5 via second edge (hereinafter referred toas “edge”) 11 which is disposed separately from damper 10 and projectsdownward.

Damper 10 has a corrugated-sheet-shaped ring structure, and extends andcontracts in response to movement of voice coil body 2. Similarly toedge 4, damper 10 is made of urethane, foamed rubber, SBR, or cloth inorder to prevent a load from being applied to movement of diaphragm 3.

An operation of a loudspeaker having such a structure during driving isdescribed hereinafter. When a voice signal is fed into the coil of voicecoil body 2, the signal interacts with the magnetic field of magneticgap 8 so that voice coil body 2 moves vertically. This movement vibratesdiaphragm 3 to transmit sound from the loudspeaker. Especially, sinceedge 11 is disposed at the outer peripheral end of damper 10, theamplitude allowance of diaphragm 3 is increased, the acoustic strain ofthe loudspeaker is suppressed, and the driving efficiency of theloudspeaker is increased.

The inner and outer peripheral ends of damper 10 are connected to voicecoil body 2 and edge 11, respectively. Damper 10 suppresses lateralvibration caused when voice coil body 2 moves. Damper 10 is structuredin a corrugated sheet shape and has elasticity so as to easily followthe movement of voice coil body 2. When the amplitude value of voicecoil body 2 is small, damper 10 having the corrugated sheet shape hardlyapplies a large load to the movement of voice coil body 2. While, whenthe amplitude value is large, damper 10 applies a large load.

In the loudspeaker of the present embodiment, the outer periphery ofdamper 10 is coupled to frame 5 via edge 11. Thanks to this structure,the movable width of voice coil body 2 increases, stress is added toedge 11 when damper 10 becomes a movable load, and edge 11 elasticallydeforms in response to this stress. Therefore, even when the vibrationamplitude value of voice coil body 2 is large, the vibration amplitudeof diaphragm 3 does not decrease, and the reduction in drivingefficiency is suppressed. In addition, the projecting directions of edge11 and edge 4 are opposite to each other. Thus, when edge 11 beginsdeforming, the load applied to the upward vibration of diaphragm 3 isnot significantly different from the load applied to the downwardvibration. Thus, increase in vibration load is suppressed by couplingdamper 10 to frame 5 via edge 11. Since edge 4 and edge 11 project tothe opposite directions on both sides of the boundary between them, theupward and downward vibration loads hardly differ from each other. Theseeffects decrease the acoustic strain of the loudspeaker of the presentembodiment.

In such a structure where damper 10 is coupled to frame 5 via edge 11,corrugated-sheet-shaped damper 10 can secure the linearity of thevibration amplitude until the movable width of voice coil body 2 isincreased to some extent. When the movable width of voice coil body 2becomes a predetermined value or more and it is difficult to secure theamplitude linearity, the elasticity of edge 11 compensates the amplitudelinearity. Therefore, the elasticity of edge 11 is preferably set largerthan that of damper 10, namely edge 11 is preferably harder than damper10.

Preferably, damper 10 and edge 11 have different elasticity, and are setso as to independently work in response to the movable width of voicecoil body 2. For that purpose, the elasticity of a portion betweendamper 10 and edge 11, specifically the elasticity of the couplingregion between damper 10 and edge 11, is preferably set larger thanthose of both damper 10 and edge 11. Namely, the region is preferablyharder than both damper 10 and edge 11. This setting of the elasticityof each component can secure the independence of damper 10 from edge 11.

For setting the elasticity of the coupling region between damper 10 andedge 11 to be larger than the elasticity of damper 10 and elasticity ofedge 11, for example, the following method is used:

-   -   employing a hard adhesive such as an acrylic adhesive in order        to stick edge 11 to damper 10;    -   integrating edge 11 and damper 10 by insert molding and        increasing the thickness of the part; or    -   sticking a reinforcing material on the coupling region.

For securing the linearity of the vibration amplitude of diaphragm 3 asa sound producing region of the loudspeaker, it is preferable not onlyto optimize the above-mentioned composite body of damper 10 and edge 11but also to define the relation between the composite body of damper 10and edge 11 and edge 4 disposed on diaphragm 3. In this relation, it isimportant how freely diaphragm 3 as a substantial sound source of theloudspeaker can vibrate vertically and uniformly. For making maximum useof the linearity of diaphragm 3 in consideration of this point, it ispreferable to set the elasticity of the composite body of damper 10 andedge 11 substantially equivalent to that of edge 4. Accordingly, edge 11is preferably set to be smaller than edge 4 as shown in FIG. 1.

In other words, damper 10 has a corrugated structure and a smallelasticity (damper 10 is soft). Therefore, by making edge 11 to besmaller than edge 4, the elasticity of edge 11 is made increased (edge11 is hardened). The elasticity of the composite body of damper 10 andedge 11 is thus set to be substantially equivalent to that of edge 4.

When voice coil body 2 as a driving point is disposed between edges 4and 11 forming fulcrums and the interval between edges 4 and 11 isincreased, lateral vibration of voice coil body 2 and diaphragm 3 issuppressed, and the acoustic strain is thus reduced. For securing theinterval between edges 4 and 11, edge 4 is preferably projected on theside opposite to damper 10, and edge 11 is preferably projected on theside opposite to diaphragm 3.

Further, as shown in FIG. 2, damper 101 may be used, and the couplingposition between edge 11 and frame 5 may be set to be lower than plate1B positioned at the upper end of magnetic circuit 1. The outerperipheral end of damper 101 is bent in a direction getting away fromdiaphragm 3. In other words, the coupling position between edge 11 andframe 5 is farther from diaphragm 3 than the end of magnetic circuit 1on the diaphragm 3 side.

In this structure, voice coil body 2 as a driving point between edges 4and 11 forming fulcrums is disposed near the center between thefulcrums, the lateral vibration of diaphragm 3 is further suppressed,and the acoustic strain is significantly reduced.

INDUSTRIAL APPLICABILITY

The present invention can reduce the acoustic strain of a loudspeaker,can improve the driving efficiency thereof, and is useful especially fora small loudspeaker.

1. A loudspeaker comprising: a frame; a magnetic circuit supported bythe frame and provided with a magnetic gap; a voice coil body disposedmovably with respect to the magnetic gap; a first edge coupled to theframe; a diaphragm, an outer peripheral end of the diaphragm beingcoupled to the frame via the first edge, and inner peripheral endthereof being coupled to the voice coil body; a second edge coupled tothe frame at a position closer to the magnetic circuit than the firstedge; and a damper disposed closer to the magnetic circuit than thediaphragm, an outer peripheral end of the damper being coupled to theframe via the second edge, an inner peripheral end of the damper beingcoupled to the voice coil body.
 2. The loudspeaker according to claim 1,wherein the first edge projects on a side opposite to a side where thedamper is disposed, and the second edge projects on a side opposite to aside where the diaphragm is disposed.
 3. The loudspeaker according toclaim 1, wherein elasticity of a composite body formed of the damper andthe second edge is substantially equivalent to elasticity of the firstedge.
 4. The loudspeaker according to claim 1, wherein elasticity of thesecond edge is larger than elasticity of the damper.
 5. The loudspeakeraccording to claim 1, wherein elasticity of a coupling portion betweenthe damper and the second edge is larger than elasticity of the damperand is larger than elasticity of the second edge.
 6. The loudspeakeraccording to claim 1, wherein an outer peripheral end of the damper isbent in a direction getting away from the diaphragm.